[NJARC] Microphone question

[Bill Zukowski]

Jules,

Tried this with my mic with no results.  However, I think the problem is 
with my microphone.

It's an Electro-Voice Model 50 which was made in the 1920s.  It's been 
packed away, with the intention of displaying it , not using it.  
However, I thought this would be a neat experiment.

Getting about 25K ohms on one side and infinity on the other was a 
definite indication of something amiss.  I gingerly dis-assembled it, 
and found the carbon granules burnt, probably from too much current.  At 
least it looks as though it was used at one time. Interesting to imagine 
when and what it was used for.

I just found the attached on the web, an old EV catalog page, which 
shows this mike using 3-5 ma. for close talking, 10-15 ma. for normal.  
This would help determining the ideal voltage and resistor value.



I may have another double button carbon mic packed away, and I'll look 
for it soon.

Let me know if Mr. Hausler has any success.

Thanks,
Bill

On 4/17/2016 9:22 PM, Bill Zukowski wrote:
> Just remember
> Reply = Poster
> Reply All = Everyone
>
> _________________________________________________________
>
>
> Jules,
>
> My original posting never appeared after 40 minutes, so I'm resending, 
> with information omitted from the first message (in red).
>
> The attached diagram (modified in red from my microphone) presentation 
> _should_ work.
>
> For the transformer use an output transformer with a tapped secondary, 
> preferably 8 ohms, tapped at 4.  Try 3 volts (polarity not important) 
> in series with a 47 ohm (I estimate) resistor to limit current.
>
> The connections are two the two screws on either side of the mic in 
> the center. The wire going to the battery from the mic is connected to 
> the housing of the microphone.
>
> This is all theoretical, but should work.  I'll try it myself tomorrow 
> afternoon and let you know how it works.
>
> With this circuit, the output will be very high compared to a normal 
> microphone (hundreds of times), so connect it after any 
> pre-amplification stages or use a pot to adjust/attenuate the signal, 
> or try a single battery.
>
> Now the legal stuff:
> /I shall not be held liable for any damages or injury, direct or 
> consequential, resulting from the use or installation of above circuit./
> Just remember
> Reply = Poster
> Reply All = Everyone
>
> _________________________________________________________
> A visitor at our museum today (J. Chris Hausler of the Morse Telegraph Club...jchausler at earthlink.net   ..)) needs to know how to set up and use a Western Electric 600A double button carbon mike. Anyone have info and a circuit?
>   Thanks,
> Jules
>
>
> Jules A. Bellisio
>    5224 Megill Road
>    Wall, New Jersey, 07727-3685, USA
>    +1 732 938 4431
>    CellPhone: +1 908 770 0552
> http://www.bellisio.com
> jules at bellisio.com
>
>
>
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